The following description relates generally to a flat panel display using an electro-optic modulator assembly, and at least one implementation relates to an electro-optic modulator (EOM) assembly capable of performing a contactless testing across the flat panel display by electro-optically obtaining a voltage distribution on the flat panel display, an apparatus and a method for contactless test of flat panel display using the same and a method for manufacturing flat panel display using the method for contactless test of the flat panel display.
Recently, flat panel displays such as LCDs (Liquid Crystal Displays), PDPs (Plasma Display Panels) and OLEDs (Organic Light Emitting Diodes), among several other display types, are widely used for displaying images.
The flat panel displays have been gradually designed to increase the display resolution to meet ceaseless requirements of brighter images. In a flat panel display, e.g., a Thin Film Transistor LCD (TFT LCD), one pixel has a width in the 0.1 mm range and one pixel is composed of 3 sub-pixels of Red (R), Green (G) and Blue (B) colors in order to perform color display, that is, each of the unit pixel parts includes a red (“R”) pixel, a green (“G”) pixel, and a blue (“B”) pixel. Resolution relates to a number of pixels used to express an image. Resolution may be used as a scale to represent precision in displaying the image. To improve resolution, display devices may use a physical method of increasing the number of pixels. In active matrix system, a TFT LCD panel thus comprises a matrix of pixels, thousands or millions of which together create an image on the display, and corresponding TFTs acting as switches individually to turn each pixel on or off, where, in other words, the TFT LCD is generally used as a switching device. For example, a TFT LCD needs 1.92 million pixels to create a 1,600×1,200 resolution, which means that the TFT LCD needs 5.76 million sub-pixels. Enhanced resolution rapidly increases the number of pixels that is needed, and as a result thereof, a fabricating process of flat panel displays requires a further sophisticated accuracy.
The enhanced accuracy that is required in the fabricating process naturally entails an increase in the likelihood of creating rejects, and as a result, requirements for testing whether each pixel has been adequately formed are also heightened. To reduce the occurrence of rejects, technical expertise with regard to an apparatus and a method for testing partially processed products (products in the course of being fabricated for flat panel displays) has been also developed.
A TFT LCD pixel structure is formed with a TFT directly deposited on a glass substrate and a transparent conductive material such as ITO (Indium Tin Oxide), where the mechanical strength thereof is relatively low, such that when the pixel may be damaged when a contact-type testing is performed where a probe pin is directly brought into contact with the pixel to test whether the pixel is normally working. Furthermore, chances are that each pixel includes an insulation layer added on a deposited structure, making it impossible to perform a contact-type testing because the probe pin cannot be contacted. Mechanical accuracy of a probe pin must be enhanced concomitant with a trend of increased pixel density, but there is a limit in processing accuracy of the probe pin, such that development has been conducted of late on apparatus and method for contactless test replaceable of the contact-type test.
The contactless test of semi-products for fabricating the flat panel displays may be obtained by making use of the electro-optic effect. The term of “electro-optic effect” is a phenomenon in which a refractive index of a material is changed by an external electric field. There are two types of electro-optical effect: one is an effect proportional to the electric field and the other is proportional to the square of the electric field. The former is called the Pockels effect: the latter is called the Kerr effect. The Pockels effect is a representative example of the electro-optic effect.
In the TFT LCD, when electricity is applied to pixels including the TFT, voltage is distributed in a predetermined pattern responsive to relative positions of a plurality of pixel electrodes distributed within the pixels. Accordingly, the voltage distribution is measured to test whether the pixels are normally operated in comparison with a normal state of voltage distribution.
A testing apparatus is illustrated in FIG. 1 to measure a voltage distribution by contactless method, wherein the apparatus includes a light source (10), an electro-optic (often termed electro-refractive) modulator (20), a device or subject under test (hereinafter referred to as DUT, where the abbreviation DUT means ‘Device Under Test’, i.e. a product to be tested.), and a camera (40), all of which are sequentially aligned on the same axial line.
Referring to FIG. 1, light emitted from the light source (10) sequentially passes the electro-optic modulator (20) and the DUT (30), where optical properties of the modulator vary in response to intensity of distribution of electric field formed between the modulator (20) and the DUT (30). The light entering from the modulator (20) is modulated in properties thereof following the pass through the modulator (20), where the modulation is obtained by the camera (40) in the form of images to understand a voltage distribution on the surface of the DUT (30).
Now, referring to FIG. 2, the electro-optic modulator (20) includes a modulation layer (21) and a conductive layer (22). The modulation layer (21) is a solid crystal having an electro-optic effect. The conductive layer (21) is mounted to provide a reference voltage surface so that an electric field can be formed relative to the voltage distribution on the surface of the DUT.
The electro-optic modulator is designed to modulate the optical characteristic of light in proportion to the intensity of electric field. The electro-optic modulator is aligned nearest to the DUT in order to minimize characteristic variances of light caused by infinitely moving objects, i.e., suspended materials and air that exist in spacing between the modulator and the DUT. The alignment of the modulator nearest to the DUT is inevitable in consideration of difficulty in detecting the modulation variances, because the intensity of electric field formed by the same voltage difference weakens as the surface of the DUT is distanced from the reference voltage surface to thereby reduce the characteristic variances of the light.
It is therefore preferable that a distance between the modulator and the DUT be shorter than a distance between voltage sources in order to prevent cross-talk from occurring between an electric field formed between the surface of the DUT and the conductive layer (22) of the modulator and an electric field formed by neighboring voltage sources on the DUT.
Meanwhile, the conductive layer (22) is conventionally formed by deposition of ITO in order to fabricate the electro-optic modulator (20) with light transmissible materials. The conductive layer (22) is very thin, weak in structural strength thereof and has difficulty in configuring terminals for electrical connections with outside.
The modulator (20) must be near the DUT to a maximum during test on the flat panel display, such that a distance between the conductive layer and the surface of the DUT is maintained very short. As a result, there is a constant likelihood of the conductive layer or a connecting terminal connected thereto being physically brought into contact with the surface of the DUT.
If contact between the conductive layer and the DUT occurs from an electrode of a DUT surface, a voltage distribution of the DUT surface may be changed by an external voltage source or a ground source connected to the conductive layer for forming a reference voltage to deteriorate the reliability of test result, and may cause an electrical damage to the DUT in certain cases.
Meanwhile, actual implementations of apparatus for contactless test entail several difficulties. Among these shortcomings, for example, the apparatus must have a structure capable of a relative movement between the modulator and the DUT for implementing a test on an entire surface of the flat panel display with one test apparatus because an area of the modulator is smaller than that of DUT (which is a flat panel display). At this time, it is imperative that the test apparatus has mechanical apparatus, such as, loading means for loading the flat panel display (which is a DUT) to the test apparatus and position correction means for aligning the flat panel display to a precise position, where the modulator and the flat panel display should not create a spatial interference with the means for performing the test.
Furthermore, although a contactless test of the modulator does not involve physical contact with the DUT, there may be many instances where the modulator is directly brought into contact with the DUT to cause damage to the DUT as the modulator is actually positioned in close proximity to the DUT. It is therefore important that such problem as the above-mentioned be prevented.
Still furthermore, it may be useful to test whether relevant process at each fabricating process is being precisely progressed in the manufacturing process of flat panel displays, and because the test on the DUT is involved with the afore-mentioned problems, there is a high likelihood of the entire manufacturing process of the flat panel displays being affected to thereby decrease the manufacturing efficiency.
The present disclosure is directed to substantially obviate one or more of the above and other problems and it is an object of the instant disclosure to provide an electro-optic modulator assembly for contactless test of flat panel display whereby the likelihood of a conductive layer or a connecting terminal being physically brought into contact with a DUT can be minimized.
Another object is to provide an electro-optic modulator assembly for contactless test of flat panel display wherein a structure is improved to facilitate formation of connecting terminal with outside.
Still another object is to provide an apparatus for contactless test of flat panel display wherein there occurs no spatial interference between each constituent element necessary for conducting contactless test of flat panel display and each constituent element for loading and position-correcting a DUT.
Still another object is to provide an apparatus for contactless test of flat panel display wherein test on an entire area of partially processed products for manufacturing flat panel display of wide area can be smoothly performed.
Still further object is to provide a method for contactless test of partially processed products for manufacturing flat panel display.
Still further object is to provide a method for manufacturing flat panel display using the method for contactless test of flat panel display whereby the flat panel display can be efficiently manufactured by performing a contactless test of partially processed products in the manufacturing process of the flat panel display.
Other objects, novel features and distinct advantageous points of the present disclosure will become more apparent by description in detailed implementations thereof with reference to the accompanying drawings.